This commit introduce a full redesign of all JS views.  We started
basically from scratch.  The goal was to unify all the various views
under a common framework, to make them testable, to make then usable in
different conditions (in studio, or in the frontend), and to make our
lives easier.

Some important points are:
- we introduced new coding guidelines (camelCase, 80 chars width, ...)
- we have a brand new testing framework (still QUnit based)
- kanban view moved to the web addon
- calendar view (formerly web_calender) moved to web as well
- the tree view was removed
- all new code should be documented

We hope that this code is the start of a new era for the Odoo web
client, we want to have a high quality codebase, well documented, well
tested, well designed.

Work done by the framework team: mostly aab, ged, chm, dmo, qsm

Since commits 2a8a17024d2b46f3f8837a8672334a7dff3abd1b and 9c68bc74827864a3c6c21be8ead1b2ed3d122d73,
the session is not started by the webclient anymore but directly by the
session service instead, and the session info is found in the DOM
instead of by RPC.

Because of that, the session is started in the frontend and other
non-backend environments which caused a JS error while trying to
load qweb (as no qweb has to be loaded). This commit makes the
session start check if it is a non-backend environment and only
initialize session info (from DOM) in that case.

With this change, form_relational_widgets will wait for the 'web.ListEditor'
module to be loaded before patching the list view.  This is particularly
important for wizards containing and editable list view.

Note that to achieve this, I had to fix a horrible hack in session.

For the need of the next commit, we have to know when making a request from an RPC call in which debug mode we are. Previously, the value was always 'true' if we were in debug mode. Now it will return 'true' if we are in simple debug mode and 'assets' if we are in the other one. (this is the current behavior for the simple WebRequest).

Why do we need to know that? When loading the settings dashboard, an rpc request to /web/dataset/call_kw to load the view is accessing the odoo.debug @property method. This value is used in the template to decide which buttons to display to activate or deactivate the debug mode.

Now that the debug URL parameter can be equal to "assets", the session
debug variable has to be updated to not only be true or false. Now, its
value is false if the debug parameter is not specified in the url and
a the URL parameter string value otherwise (or 1 if the value is an
empty string).

Also modify all redirection which kept the debug mode to also keep
=assets. Use the $.param.querystring function.

It is already in the web client page source (or more precisely, in the
assets_backent bundle)

This commit introduces a mechanism to add information into the session
from a different module, without having to fetch it manually with a rpc.
This is intended to be used with small pieces of info required at the
start of the web client, such as currency informations.

To add information to the session, one can simply inherit from ir.http
and modify the session_info method.